In modern aircraft, various types of energy transmission are used for supplying aircraft systems. Apart from electrical energy, the main engines also supply pneumatic and hydraulic energy to the aircraft, using corresponding media. As a rule, the auxiliary power unit supplies pneumatic and electrical energy for starting the engines and for operating the aircraft both on the ground and in the event of an emergency.
The hydraulic and the bleed air systems, which extend along large stretches through the aircraft, are associated with a host of disadvantages. Bleed air systems require considerable construction expenditure, e.g. for operating the pneumatic valves and intermediate cooling devices. In such arrangements the maintenance effort on the engine and in the aircraft is considerable. The efficiency of the cabin air conditioning systems, which are operated with bleed air, is low. The hydraulic systems of the aircraft require considerable maintenance effort.
The energy required for operating (future) fully-electrical onboard systems can be provided by several generators driven by the engine. However, as a rule these additional generators cause the device carrier to be exposed to correspondingly heavy mechanical loads. As an alternative to installation on a device carrier, the engine generators can be directly coupled to the engine shafts. However, both concepts result in a heavy and inefficient engine that is difficult to regulate and furthermore is not easy to maintain.
There may be a need to state improved energy generation on board aircraft.